The present invention relates to and has essentially for a subject matter a method for manufacturing tubes particularly of paperboard or cardboard by helical winding of a strip or of several strips of paper, and a machine for carrying out the said method.
It is already known to manufacture paperboard tubes by helical winding of one or several pre-pasted paper or paperboard strips on a stationary mandrel. In this method, the tube in course of formation is driven in rotation about the stationary mandrel.
In this known method, the paper or paperboard strip or the multiple paper or paperboard strips partially overlap and are transversely shifted with respect to one another so as to form a web or the like. Thus, the winding pitch of a paper strip will be a function of the width of the said paper strip, of the mandrel diameter and of the value of the winding angle of the said paper strip formed between the paper strip pay-out direction and the longitudinal axis of the stationary mandrel. Therefore, the characteristics of the manufactured tube depend on the wound paper, but also on the paper strip winding angle.
In order to carry out this known method, use is made of a manufacturing machine comprising a stationary frame bearing the stationary mandrel and a movable frame allowing the paper strip or the web of paper strips to be paid out onto the stationary mandrel along a pay-out direction defined by the desired winding angle. To this end, the movable frame of the known manufacturing machine is mounted so as to swivel round a vertical axis located in the vertical plane of the horizontal longitudinal axis of the mandrel. At the beginning of each manufacturing cycle, the winding angle i.e. the pay-out direction of the paper strips, was adjusted by manually displacing the movable frame.
This method suffers from many drawbacks and requires a protracted, laborious and inaccurate adjustment - to within several degrees - of the winding angle, due particularly to the large dimensions of the movable frame. Moreover, the said adjustment was empirical for it was not possible to accurately measure the angle formed between the fictive swivelling axis of the movable frame and the longitudinal axis of the mandrel. In addition, since the adjustment had to be performed manually, it entailed much labour cost.